Nginx中 $host $http_host $proxy_host的区别

变量	值来源	是否显示端口	说明
$host	按照请求行中的Host > 请求头中的Host > server_name 的值优先级获取	否	"Host:port"显示值为a:b的时候，只显示a
$http_host	请求头中的Host	是	"Host:port"，port存在就显示，请求头中Host是多少 $http_host就是多少
$proxy_host	proxy_pass 指定的地址	是（默认80不显示）	"Host:port" proxy_pass指定的 "Host:port"，当port为80的时候只有“Host”，其它端口，正常显示为 “Host:port”

官方文档说明

ngx_http_core_module 模块变量

$host 按以下优先顺序排列：请求行中的主机名，或 “Host ”请求头字段中的主机名，或与请求匹配的服务器名(server_name)

$http_ name 任意请求标头字段；变量名的最后一部分是转换为小写的字段名，破折号由下划线代替

如:

请求中有

Host: example.com
User-Agent: curl/7.68.0
X-Forwarded-For: 1.2.3.4

就可以使用

$http_host
$http_user_agent
$http_x_forwarded_for

ngx_http_proxy_module 模块变量

$proxy_host : proxy_pass指令中指定的代理服务器的名称和端口；

测试携带端口和不携带端口的变量值

通过Nginx日志，查看这三个变量的值

log_format hosttest '$host|$http_host|$proxy_host';

server {
        listen 8888 default_server;
        listen 80;
        server_name www.example.com;
        charset utf-8;

        location /test {
            proxy_pass http://192.168.100.100:9200;
            access_log /var/log/nginx/test.log hosttest;
        }

        location /80 {
            proxy_pass http://192.168.100.100;
            access_log /var/log/nginx/test.log hosttest;
        }

        access_log /var/log/nginx/static_access.log main;
        error_log /var/log/nginx/static_error.log;
}

宿主机，在 /etc/hosts文件添加Hosts解析

192.168.1.236    www.example.com

通过curl测试

测试请求

curl www.example.com:8888/80
curl www.example.com:8888/test
curl www.example.com/80
curl www.example.com/test
curl www.example.com:80/80
curl www.example.com:80/test

对应日志

www.example.com|www.example.com:8888|192.168.100.100
www.example.com|www.example.com:8888|192.168.100.100:9200
www.example.com|www.example.com|192.168.100.100
www.example.com|www.example.com|192.168.100.100:9200
www.example.com|www.example.com|192.168.100.100
www.example.com|www.example.com|192.168.100.100:9200

结果

请求地址	请求地址携带端口	proxy_pass	$host	$http_host	$proxy_host
www.example.com:8888/80	是	http://192.168.100.100	www.example.com	www.example.com:8888	192.168.100.100
www.example.com:8888/test	是	http://192.168.100.100:9200	www.example.com	www.example.com:8888	192.168.100.100:9200
www.example.com/80	否	http://192.168.100.100	www.example.com	www.example.com	192.168.100.100
www.example.com/test	否	http://192.168.100.100:9200	www.example.com	www.example.com	192.168.100.100:9200
www.example.com:80/80	是	http://192.168.100.100:80	www.example.com	www.example.com	192.168.100.100
www.example.com:80/test	是	http://192.168.100.100:9200	www.example.com	www.example.com	192.168.100.100:9200

1.$host 与请求行中的Host、请求头中的Host、匹配的server_name的值有关，但是在这里体现的不明显。

因为通过curl请求，请求行中不携带Host，自动在请求头中添加Host，且会自动将www.example.com:80中的端口删除，使请求头中的Host为www.example.com，不过请求头中携带80端口，$host也不会携带端口，比如：

$ curl www.example.com:80/80 -v -H "Host: www.example.com:80"
*   Trying 192.168.1.236...
* TCP_NODELAY set
* Connected to www.example.com (192.168.1.236) port 80 (#0)
> GET /80 HTTP/1.1
> Host: www.example.com:80
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 404 Not Found
< Date: Mon, 12 May 2025 09:29:23 GMT
< Content-Type: text/html; charset=utf-8
< Content-Length: 150
< Connection: keep-alive
< Server: SwiftWaf
<
<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>openresty</center>
</body>
</html>
* Connection #0 to host www.example.com left intact

日志

www.example.com|www.example.com:80|192.168.100.100

2.$http_host 请求头中的Host是多少，这里就是多少。

同样的原因，在请求curl www.example.com:80/80的时候，请求头中的Host为www.example.com，curl自动将端口删除了，这里表示的不够明显，如果请求头中的是www.example.com:80，那么$http_host的值就是www.example.com:80。

3.$proxy_host 与 $proxy_pass有关，转发非80端口，为Host:Port，转发80端口，不管携带不携带端口，都是Host

注意：

通过curl命令测试，请求行中都不包含Host，因为请求行是GET /80 HTTP/1.1，而不是GET http://www.example.com:8888/80 HTTP/1.1

$ curl www.example.com:8888/80 -v
*   Trying 192.168.1.236...
* TCP_NODELAY set
* Connected to www.example.com (192.168.1.236) port 8888 (#0)
> GET /80 HTTP/1.1
> Host: www.example.com:8888
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 404 Not Found
< Date: Mon, 12 May 2025 09:19:14 GMT
< Content-Type: text/html; charset=utf-8
< Content-Length: 150
< Connection: keep-alive
< Server: SwiftWaf
<
<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>openresty</center>
</body>
</html>
* Connection #0 to host www.example.com left intact

可以通过nc模拟请求行中携带Host的请求，比如

# 请求行携带Host，请求头不携带Host
printf "GET http://www.example.com:8888/80 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 80

# 请求行携带Host，请求头携带host
printf "GET http://www.example.com:8888/80 HTTP/1.0\r\nHost: foo.com\r\n\r\n" | nc 192.168.1.236 80

通过nc测试

# 请求行携带Host，请求头不携带Host
printf "GET http://www.example.com:8888/80 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 80

# 请求行携带Host，请求头携带host
printf "GET http://www.example.com:8888/80 HTTP/1.0\r\nHost: foo.com\r\n\r\n" | nc 192.168.1.236 80

# 请求行不携带Host，请求头不携带Host
printf "GET /80 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 80

Nginx配置

log_format hosttest '$host|$http_host|$proxy_host';

server {
        listen 8888 default_server;
        listen 80;
        server_name www.example.com;
        charset utf-8;

        location /test1 {
            proxy_pass http://192.168.100.100:8080;
            access_log /var/log/nginx/test.log hosttest;
        }

        location /test2 {
            proxy_pass http://192.168.100.100;
            access_log /var/log/nginx/test.log hosttest;
        }

        location /test3 {
            proxy_pass http://192.168.100.100:80;
            access_log /var/log/nginx/test.log hosttest;
        }

        access_log /var/log/nginx/static_access.log main;
        error_log /var/log/nginx/static_error.log;
}

测试命令

# 请求行携带Host 不同，请求头不携带Host，接口相同
printf "GET http://www.example.com:8888/test1 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 8888
printf "GET http://www.example.com/test1 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 8888
printf "GET http://www.example.com:80/test1 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 8888

# 请求行不携带Host，请求头携带host 不同，接口相同
printf "GET /test1 HTTP/1.0\r\nHost: www.example.com:8888\r\n\r\n" | nc 192.168.1.236 8888
printf "GET /test1 HTTP/1.0\r\nHost: www.example.com\r\n\r\n" | nc 192.168.1.236 8888
printf "GET /test1 HTTP/1.0\r\nHost: www.example.com:80\r\n\r\n" | nc 192.168.1.236 8888

# 请求行不携带Host，请求头不携带Host，接口不同
printf "GET /test1 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 8888
printf "GET /test2 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 8888
printf "GET /test3 HTTP/1.0\r\n\r\n" | nc 192.168.1.236 8888

日志

www.example.com|-|192.168.100.100:8080
www.example.com|-|192.168.100.100:8080
www.example.com|-|192.168.100.100:8080



www.example.com|www.example.com:8888|192.168.100.100:8080
www.example.com|www.example.com|192.168.100.100:8080
www.example.com|www.example.com:80|192.168.100.100:8080



www.example.com|-|192.168.100.100:8080
www.example.com|-|192.168.100.100
www.example.com|-|192.168.100.100

请求	请求行中Host	请求头中Host	proxy_pass	$host	$http_host	$proxy_host
GET http://www.example.com:8888/test1 HTTP/1.0\r\n\r\n	www.example.com:8888	无	http://192.168.100.100:8080	www.example.com (请求行中的Host)	-	192.168.100.100:8080
GET http://www.example.com/test1 HTTP/1.0\r\n\r\n	www.example.com	无	http://192.168.100.100:8080	www.example.com (请求行中的Host)	-	192.168.100.100:8080
GET http://www.example.com:80/test1 HTTP/1.0\r\n\r\n	www.example.com:80	无	http://192.168.100.100:8080	www.example.com (请求行中的Host)	-	192.168.100.100:8080
GET /test1 HTTP/1.0\r\nHost: www.example.com:8888\r\n\r\n	无	www.example.com:8888	http://192.168.100.100:8080	www.example.com (请求头中的Host)	www.example.com:8888	192.168.100.100:8080
GET /test1 HTTP/1.0\r\nHost: www.example.com\r\n\r\n	无	www.example.com	http://192.168.100.100:8080	www.example.com (请求头中的Host)	www.example.com	192.168.100.100:8080
GET /test1 HTTP/1.0\r\nHost: www.example.com:80\r\n\r\n	无	www.example.com:80	http://192.168.100.100:8080	www.example.com (请求头中的Host)	www.example.com:80	192.168.100.100:8080
GET /test1 HTTP/1.0\r\n\r\n	无	无	http://192.168.100.100:8080	www.example.com (server_name)	-	192.168.100.100:8080
GET /test2 HTTP/1.0\r\n\r\n	无	无	http://192.168.100.100	www.example.com (server_name)	-	192.168.100.100
GET /test3 HTTP/1.0\r\n\r\n	无	无	http://192.168.100.100:80	www.example.com (server_name)	-	192.168.100.100 (携带80不显示)

测试$host中的优先级

进一步测试 $host，验证是否是官方说的顺序:

请求行中的主机名 > “Host ”请求头字段中的主机名 > 与请求匹配的服务器名(server_name)

设置一个调试配置

server {
        listen 80;
        server_name _;

        location /test {
            return 200 "$host\n";
        }
}

测试场景1：手动构造 Request Line 带 Host（非常规，需工具支持）

printf "GET http://foo.com/test HTTP/1.1\r\nHost: bar.com\r\n\r\n" | nc 192.168.1.236 80

返回的$host是foo.com，说明Nginx优先使用请求行中的Host

通过curl -v 'http://www.example.com/test' -H "Host: foo.com"测试失败

curl -v 'http://www.example.com/test' -H "Host: foo.com"
*   Trying 192.168.1.236...
* TCP_NODELAY set
* Connected to www.example.com (192.168.1.236) port 80 (#0)
> GET /test HTTP/1.1
> Host: foo.com
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Mon, 12 May 2025 08:54:41 GMT
< Content-Type: application/octet-stream
< Content-Length: 8
< Connection: keep-alive
< Server: SwiftWaf
<
foo.com
* Connection #0 to host www.example.com left intact

原因是：

curl -v 'http://www.example.com/test' 会解析域名，填入 Host 头，但请求行是：

GET /test HTTP/1.1

而不是

GET http://www.example.com/test HTTP/1.1

所以你的 $host 来源仍然是 Host 头字段，不是 request line 中的 host。

真正测试 “请求行中的 host 优先级” 的方法：

你需要手工伪造带绝对 URI 的 request line，例如使用 nc：

printf "GET http://www.example.com/test HTTP/1.1\r\nHost: foo.com\r\n\r\n" | nc 192.168.1.236 80

测试结果

$ printf "GET http://www.example.com/test HTTP/1.1\r\nHost: foo.com\r\n\r\n" | nc 192.168.1.236 80
HTTP/1.1 200 OK
Date: Mon, 12 May 2025 08:56:40 GMT
Content-Type: application/octet-stream
Content-Length: 16
Connection: keep-alive
Server: SwiftWaf

www.example.com



^C

可以看到$host返回www.example.com，证明 Nginx 确实优先使用了请求行中的 host。

测试场景2：请求行不添加host，请求头添加 Host

curl 会自动添加Host，实际请求行是GET /test HTTP/1.1，不包含Host，请求头中包含HostHost: www.example.com。

最终$host返回请求头中的Hostwww.example.com，说明请求头中的Host 优先级高于匹配的server_name值。

$ curl -v http://www.example.com/test
*   Trying 192.168.1.236...
* TCP_NODELAY set
* Connected to www.example.com (192.168.1.236) port 80 (#0)
> GET /test HTTP/1.1
> Host: www.example.com
> User-Agent: curl/7.58.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Mon, 12 May 2025 09:06:53 GMT
< Content-Type: application/octet-stream
< Content-Length: 16
< Connection: keep-alive
< Server: SwiftWaf
<
www.example.com
* Connection #0 to host www.example.com left intact

通过nc模拟请求行不添加host，请求头添加Host的场景

printf "GET /test HTTP/1.1\r\nHost: foo.com\r\n\r\n" | nc 192.168.1.236 80

结果

$ printf "GET /test HTTP/1.1\r\nHost: foo.com\r\n\r\n" | nc 192.168.1.236 80
HTTP/1.1 200 OK
Date: Mon, 12 May 2025 09:04:48 GMT
Content-Type: application/octet-stream
Content-Length: 8
Connection: keep-alive
Server: SwiftWaf

foo.com

请求行中不包含Host，请求头包含Host，$host返回请求头中包含的Hostfoo.com，没有返回server_name中的值，说明请求头中的Host优先级高于server_name的名称。

测试场景3：完全不传 Host 头（curl 会自动加）

用 nc（netcat）构造请求来模拟无 Host 请求：

printf "GET /test HTTP/1.0\r\n\r\n" | nc 192.168.1.236 80

测试结果

$ printf "GET /test HTTP/1.0\r\n\r\n" | nc 192.168.1.236 80
HTTP/1.1 200 OK
Date: Mon, 12 May 2025 08:58:31 GMT
Content-Type: application/octet-stream
Content-Length: 2
Connection: close
Server: SwiftWaf

_

通过nc模拟请求行中没有host，请求头中不包含Host的请求，结果 $host返回server_name的值 _。说明server_name优先级最低

如果server_name为www.example.com，则$host返回www.example.com,比如：

server {
        listen 80 default_server;
        server_name www.example.com;

        location /test {
            return 200 "$host\n";
        }
}

测试

$ printf "GET /test HTTP/1.0\r\n\r\n" | nc 192.168.1.236 80
HTTP/1.1 200 OK
Date: Mon, 12 May 2025 09:02:44 GMT
Content-Type: application/octet-stream
Content-Length: 16
Connection: close
Server: SwiftWaf

www.example.com

注意：

如果使用 HTTP/1.1 协议发起不包含Host的请求，Nginx会直接返回 400 Bad Request（这是符合 HTTP/1.1 标准的 —— 必须带 Host）。

HTTP/1.0 没有这个强制要求，因此请求成功。

$ printf "GET /test HTTP/1.1\r\n\r\n" | nc 192.168.1.236 80
HTTP/1.1 400 Bad Request
Date: Mon, 12 May 2025 08:58:36 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 154
Connection: close
Server: SwiftWaf

<html>
<head><title>400 Bad Request</title></head>
<body>
<center><h1>400 Bad Request</h1></center>
<hr><center>openresty</center>
</body>
</html>